This invention relates to a thermoplastic device for overlaying blood or cellular suspension over a volume of density gradient contained in a centrifuge tube, such as a conical centrifuge tube, a round bottom tube, an ultra centrifuge tube, or any other type of centrifuge tube.
The isolation and preparation of leukocytes, more generally referred to as “white blood cells” (WBC's), from whole blood or cellular suspension using a density gradient is generally the first technique to be carried out in any immunological experiment. WBC's are the main components of our immune system and thus are the main target for experimentation.
While the density gradient protocol is efficient at yielding a high percentage of WBC's from a sample, it is time consuming, messy, and requires hours of hands-on training. The most time consuming part of the density gradient protocol is the “overlay”, where blood or cellular suspension is carefully poured over the surface of the density gradient as to prevent any mixing of the two liquids. Two separate layers must be formed with minimal mixing in order to yield a sufficient number of cells. The overlay is completed by holding two centrifuge tubes together, one with density gradient and one with blood or cellular suspension, and slowly pouring the blood or cellular suspension over the density gradient liquid.
There are several major drawbacks to the overlay method in the density gradient protocol. Primarily, the protocol depends on the lab technician to judge how fast or slow to pour the blood or cellular suspension onto the density gradient liquid. This dependence on human technique frequently results in spills, mixing the blood/cellular suspension with the density gradient, or total loss of sample. In addition, the overlay method is time consuming and tedious. The majority of the time spent isolating WBC's is spent on the overlay method. Larger experiments that require a lot of WBC's are split into multiple experiments because there is simply not enough time in the day to overlay a large volume of blood or cellular suspension.
Clearly, then, there is a need for a device used to overlay blood or cellular suspension that can be used by any lab technician without prior training and that can speed up the overlay process. Such a device would virtually eliminate prior training or human error in the overlay process, dramatically reduce the time it takes to overlay, and increase yield by reducing spills.
Further, such a needed device would be relatively easy to manufacture on a large scale, use, dispose, and would allow much larger experiments to be performed. The present invention fulfills these needs and provides further related advantages.